Blood Volume in the Human Body and Its Main Functions

Blood is one of the body’s most important fluids, supplying cells with the substances they need. It consists of plasma, red blood cells, and white blood cells, and plays a key role in transporting oxygen, hormones, and nutrients throughout the body.

An adult human body contains about 4.5–5.5 liters of blood on average. This is roughly 8% of total body weight. Depending on body structure and muscle mass, men may have a slightly larger blood volume than women.

Blood circulates through the body with the help of the heart and moves through blood vessels — arteries, veins, and capillaries. Capillaries allow blood to reach even the smallest tissues and cells.

Blood not only carries useful substances but also helps remove waste products produced by cells. This process works closely with the lymphatic system. Lymph collects excess fluid and some waste products from tissues and carries them through the lymph nodes.